For quite some time, designers of competitive as well as recreational bicycles have sought to design bicycle components in a manner that minimizes the weight of the individual component without significantly sacrificing the strength of the component. It is axiomatic that if weight can be reduced without decreasing strength, a bicycle can be provided that will allow the rider to achieve substantially better performance without increasing the likelihood of failure of the bicycle. This enhanced performance translates to greater speed and/or duration or a reduction of fatigue experienced by the rider over any given course for any period of time.
In this past, attempts to make bicycles lighter have concentrated on the fabrication of bicycle components from stronger and lighter materials such as aluminum. These materials are utilized not only in constructing the wheels of the bicycle but also in construction of the frame and of various other components.
Great efforts are currently under way in the bicycle manufacturing industry to design bicycles that are light in weight without sacrificing strength.
One component that has been subject to considerable design research is the crank arm. Commonly, a bicycle includes two crank arms which are located approximately 180.degree. apart relative to a hub bearing assembly. The outer end of each crank arm is connected to a pedal which is used by the rider to apply a force which results in movement of the bicycle.
Builders of bicycles have repeatedly attempted to redesign the crank to allow them to be fabricated of stronger, lighter material. However, since the crank arms directly transfer the muscle power of the rider into a propelling force of the bicycle, the crank arms are subjected to a significant amount of torque and bending moment. Because it is common for a bicycle to be operated for an extended period of time over varied terrain, the continuous stress applied over such periods of time have resulted in failure of the crank arms.
Accordingly, there is a need to construct a crank arm for bicycle having a reduced weight while at the same time being strong enough to minimize the likelihood of failure despite high torsional and bending stresses applied over an extended period of time.